#ifndef CRYPTOPP_GFPCRYPT_H
#define CRYPTOPP_GFPCRYPT_H

/** \file
	Implementation of schemes based on DL over GF(p)
 */

#include "pubkey.h"
#include "modexppc.h"
#include "sha.h"
#include "algparam.h"
#include "asn.h"
#include "smartptr.h"
#include "hmac.h"

#include <limits.h>

NAMESPACE_BEGIN(CryptoPP)

CRYPTOPP_DLL_TEMPLATE_CLASS DL_GroupParameters<Integer>;

//! _
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE DL_GroupParameters_IntegerBased : public ASN1CryptoMaterial<DL_GroupParameters<Integer> >
{
    typedef DL_GroupParameters_IntegerBased ThisClass;
    
public:
    void Initialize(const DL_GroupParameters_IntegerBased &params)
    {Initialize(params.GetModulus(), params.GetSubgroupOrder(), params.GetSubgroupGenerator());}
    void Initialize(RandomNumberGenerator &rng, unsigned int pbits)
    {GenerateRandom(rng, MakeParameters("ModulusSize", (int)pbits));}
    void Initialize(const Integer &p, const Integer &g)
    {SetModulusAndSubgroupGenerator(p, g); SetSubgroupOrder(ComputeGroupOrder(p)/2);}
    void Initialize(const Integer &p, const Integer &q, const Integer &g)
    {SetModulusAndSubgroupGenerator(p, g); SetSubgroupOrder(q);}
    
    // ASN1Object interface
    void BERDecode(BufferedTransformation &bt);
    void DEREncode(BufferedTransformation &bt) const;
    
    // GeneratibleCryptoMaterial interface
    /*! parameters: (ModulusSize, SubgroupOrderSize (optional)) */
    void GenerateRandom(RandomNumberGenerator &rng, const NameValuePairs &alg);
    bool GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const;
    void AssignFrom(const NameValuePairs &source);
    
    // DL_GroupParameters
    const Integer & GetSubgroupOrder() const {return m_q;}
    Integer GetGroupOrder() const {return GetFieldType() == 1 ? GetModulus()-Integer::One() : GetModulus()+Integer::One();}
    bool ValidateGroup(RandomNumberGenerator &rng, unsigned int level) const;
    bool ValidateElement(unsigned int level, const Integer &element, const DL_FixedBasePrecomputation<Integer> *precomp) const;
    bool FastSubgroupCheckAvailable() const {return GetCofactor() == 2;}
    void EncodeElement(bool reversible, const Element &element, byte *encoded) const
    {element.Encode(encoded, GetModulus().ByteCount());}
    unsigned int GetEncodedElementSize(bool reversible) const {return GetModulus().ByteCount();}
    Integer DecodeElement(const byte *encoded, bool checkForGroupMembership) const;
    Integer ConvertElementToInteger(const Element &element) const
    {return element;}
    Integer GetMaxExponent() const;
    static std::string CRYPTOPP_API StaticAlgorithmNamePrefix() {return "";}
    
    OID GetAlgorithmID() const;
    
    virtual const Integer & GetModulus() const =0;
    virtual void SetModulusAndSubgroupGenerator(const Integer &p, const Integer &g) =0;
    
    void SetSubgroupOrder(const Integer &q)
    {m_q = q; ParametersChanged();}
    
protected:
    Integer ComputeGroupOrder(const Integer &modulus) const
    {return modulus-(GetFieldType() == 1 ? 1 : -1);}
    
    // GF(p) = 1, GF(p^2) = 2
    virtual int GetFieldType() const =0;
    virtual unsigned int GetDefaultSubgroupOrderSize(unsigned int modulusSize) const;
    
private:
    Integer m_q;
};

//! _
template <class GROUP_PRECOMP, class BASE_PRECOMP = DL_FixedBasePrecomputationImpl<CPP_TYPENAME GROUP_PRECOMP::Element> >
class CRYPTOPP_NO_VTABLE DL_GroupParameters_IntegerBasedImpl : public DL_GroupParametersImpl<GROUP_PRECOMP, BASE_PRECOMP, DL_GroupParameters_IntegerBased>
{
    typedef DL_GroupParameters_IntegerBasedImpl<GROUP_PRECOMP, BASE_PRECOMP> ThisClass;
    
public:
    typedef typename GROUP_PRECOMP::Element Element;
    
    // GeneratibleCryptoMaterial interface
    bool GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
    {return GetValueHelper<DL_GroupParameters_IntegerBased>(this, name, valueType, pValue).Assignable();}
    
    void AssignFrom(const NameValuePairs &source)
    {AssignFromHelper<DL_GroupParameters_IntegerBased>(this, source);}
    
    // DL_GroupParameters
    const DL_FixedBasePrecomputation<Element> & GetBasePrecomputation() const {return this->m_gpc;}
    DL_FixedBasePrecomputation<Element> & AccessBasePrecomputation() {return this->m_gpc;}
    
    // IntegerGroupParameters
    const Integer & GetModulus() const {return this->m_groupPrecomputation.GetModulus();}
    const Integer & GetGenerator() const {return this->m_gpc.GetBase(this->GetGroupPrecomputation());}
    
    void SetModulusAndSubgroupGenerator(const Integer &p, const Integer &g)		// these have to be set together
    {this->m_groupPrecomputation.SetModulus(p); this->m_gpc.SetBase(this->GetGroupPrecomputation(), g); this->ParametersChanged();}
    
    // non-inherited
    bool operator==(const DL_GroupParameters_IntegerBasedImpl<GROUP_PRECOMP, BASE_PRECOMP> &rhs) const
    {return GetModulus() == rhs.GetModulus() && GetGenerator() == rhs.GetGenerator() && this->GetSubgroupOrder() == rhs.GetSubgroupOrder();}
    bool operator!=(const DL_GroupParameters_IntegerBasedImpl<GROUP_PRECOMP, BASE_PRECOMP> &rhs) const
    {return !operator==(rhs);}
};

CRYPTOPP_DLL_TEMPLATE_CLASS DL_GroupParameters_IntegerBasedImpl<ModExpPrecomputation>;

//! GF(p) group parameters
class CRYPTOPP_DLL DL_GroupParameters_GFP : public DL_GroupParameters_IntegerBasedImpl<ModExpPrecomputation>
{
public:
    // DL_GroupParameters
    bool IsIdentity(const Integer &element) const {return element == Integer::One();}
    void SimultaneousExponentiate(Element *results, const Element &base, const Integer *exponents, unsigned int exponentsCount) const;
    
    // NameValuePairs interface
    bool GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
    {
        return GetValueHelper<DL_GroupParameters_IntegerBased>(this, name, valueType, pValue).Assignable();
    }
    
    // used by MQV
    Element MultiplyElements(const Element &a, const Element &b) const;
    Element CascadeExponentiate(const Element &element1, const Integer &exponent1, const Element &element2, const Integer &exponent2) const;
    
protected:
    int GetFieldType() const {return 1;}
};

//! GF(p) group parameters that default to same primes
class CRYPTOPP_DLL DL_GroupParameters_GFP_DefaultSafePrime : public DL_GroupParameters_GFP
{
public:
    typedef NoCofactorMultiplication DefaultCofactorOption;
    
protected:
    unsigned int GetDefaultSubgroupOrderSize(unsigned int modulusSize) const {return modulusSize-1;}
};

//! GDSA algorithm
template <class T>
class DL_Algorithm_GDSA : public DL_ElgamalLikeSignatureAlgorithm<T>
{
public:
    static const char * CRYPTOPP_API StaticAlgorithmName() {return "DSA-1363";}
    
    void Sign(const DL_GroupParameters<T> &params, const Integer &x, const Integer &k, const Integer &e, Integer &r, Integer &s) const
    {
        const Integer &q = params.GetSubgroupOrder();
        r %= q;
        Integer kInv = k.InverseMod(q);
        s = (kInv * (x*r + e)) % q;
        assert(!!r && !!s);
    }
    
    bool Verify(const DL_GroupParameters<T> &params, const DL_PublicKey<T> &publicKey, const Integer &e, const Integer &r, const Integer &s) const
    {
        const Integer &q = params.GetSubgroupOrder();
        if (r>=q || r<1 || s>=q || s<1)
            return false;
        
        Integer w = s.InverseMod(q);
        Integer u1 = (e * w) % q;
        Integer u2 = (r * w) % q;
        // verify r == (g^u1 * y^u2 mod p) mod q
        return r == params.ConvertElementToInteger(publicKey.CascadeExponentiateBaseAndPublicElement(u1, u2)) % q;
    }
};

CRYPTOPP_DLL_TEMPLATE_CLASS DL_Algorithm_GDSA<Integer>;

//! NR algorithm
template <class T>
class DL_Algorithm_NR : public DL_ElgamalLikeSignatureAlgorithm<T>
{
public:
    static const char * CRYPTOPP_API StaticAlgorithmName() {return "NR";}
    
    void Sign(const DL_GroupParameters<T> &params, const Integer &x, const Integer &k, const Integer &e, Integer &r, Integer &s) const
    {
        const Integer &q = params.GetSubgroupOrder();
        r = (r + e) % q;
        s = (k - x*r) % q;
        assert(!!r);
    }
    
    bool Verify(const DL_GroupParameters<T> &params, const DL_PublicKey<T> &publicKey, const Integer &e, const Integer &r, const Integer &s) const
    {
        const Integer &q = params.GetSubgroupOrder();
        if (r>=q || r<1 || s>=q)
            return false;
        
        // check r == (m_g^s * m_y^r + m) mod m_q
        return r == (params.ConvertElementToInteger(publicKey.CascadeExponentiateBaseAndPublicElement(s, r)) + e) % q;
    }
};

/*! DSA public key format is defined in 7.3.3 of RFC 2459. The
	private key format is defined in 12.9 of PKCS #11 v2.10. */
template <class GP>
class DL_PublicKey_GFP : public DL_PublicKeyImpl<GP>
{
public:
    void Initialize(const DL_GroupParameters_IntegerBased &params, const Integer &y)
    {this->AccessGroupParameters().Initialize(params); this->SetPublicElement(y);}
    void Initialize(const Integer &p, const Integer &g, const Integer &y)
    {this->AccessGroupParameters().Initialize(p, g); this->SetPublicElement(y);}
    void Initialize(const Integer &p, const Integer &q, const Integer &g, const Integer &y)
    {this->AccessGroupParameters().Initialize(p, q, g); this->SetPublicElement(y);}
    
    // X509PublicKey
    void BERDecodePublicKey(BufferedTransformation &bt, bool, size_t)
    {this->SetPublicElement(Integer(bt));}
    void DEREncodePublicKey(BufferedTransformation &bt) const
    {this->GetPublicElement().DEREncode(bt);}
};

//! DL private key (in GF(p) groups)
template <class GP>
class DL_PrivateKey_GFP : public DL_PrivateKeyImpl<GP>
{
public:
    void Initialize(RandomNumberGenerator &rng, unsigned int modulusBits)
    {this->GenerateRandomWithKeySize(rng, modulusBits);}
    void Initialize(RandomNumberGenerator &rng, const Integer &p, const Integer &g)
    {this->GenerateRandom(rng, MakeParameters("Modulus", p)("SubgroupGenerator", g));}
    void Initialize(RandomNumberGenerator &rng, const Integer &p, const Integer &q, const Integer &g)
    {this->GenerateRandom(rng, MakeParameters("Modulus", p)("SubgroupOrder", q)("SubgroupGenerator", g));}
    void Initialize(const DL_GroupParameters_IntegerBased &params, const Integer &x)
    {this->AccessGroupParameters().Initialize(params); this->SetPrivateExponent(x);}
    void Initialize(const Integer &p, const Integer &g, const Integer &x)
    {this->AccessGroupParameters().Initialize(p, g); this->SetPrivateExponent(x);}
    void Initialize(const Integer &p, const Integer &q, const Integer &g, const Integer &x)
    {this->AccessGroupParameters().Initialize(p, q, g); this->SetPrivateExponent(x);}
};

//! DL signing/verification keys (in GF(p) groups)
struct DL_SignatureKeys_GFP
{
    typedef DL_GroupParameters_GFP GroupParameters;
    typedef DL_PublicKey_GFP<GroupParameters> PublicKey;
    typedef DL_PrivateKey_GFP<GroupParameters> PrivateKey;
};

//! DL encryption/decryption keys (in GF(p) groups)
struct DL_CryptoKeys_GFP
{
    typedef DL_GroupParameters_GFP_DefaultSafePrime GroupParameters;
    typedef DL_PublicKey_GFP<GroupParameters> PublicKey;
    typedef DL_PrivateKey_GFP<GroupParameters> PrivateKey;
};

//! provided for backwards compatibility, this class uses the old non-standard Crypto++ key format
template <class BASE>
class DL_PublicKey_GFP_OldFormat : public BASE
{
public:
    void BERDecode(BufferedTransformation &bt)
    {
        BERSequenceDecoder seq(bt);
        Integer v1(seq);
        Integer v2(seq);
        Integer v3(seq);
        
        if (seq.EndReached())
        {
            this->AccessGroupParameters().Initialize(v1, v1/2, v2);
            this->SetPublicElement(v3);
        }
        else
        {
            Integer v4(seq);
            this->AccessGroupParameters().Initialize(v1, v2, v3);
            this->SetPublicElement(v4);
        }
        
        seq.MessageEnd();
    }
    
    void DEREncode(BufferedTransformation &bt) const
    {
        DERSequenceEncoder seq(bt);
        this->GetGroupParameters().GetModulus().DEREncode(seq);
        if (this->GetGroupParameters().GetCofactor() != 2)
            this->GetGroupParameters().GetSubgroupOrder().DEREncode(seq);
        this->GetGroupParameters().GetGenerator().DEREncode(seq);
        this->GetPublicElement().DEREncode(seq);
        seq.MessageEnd();
    }
};

//! provided for backwards compatibility, this class uses the old non-standard Crypto++ key format
template <class BASE>
class DL_PrivateKey_GFP_OldFormat : public BASE
{
public:
    void BERDecode(BufferedTransformation &bt)
    {
        BERSequenceDecoder seq(bt);
        Integer v1(seq);
        Integer v2(seq);
        Integer v3(seq);
        Integer v4(seq);
        
        if (seq.EndReached())
        {
            this->AccessGroupParameters().Initialize(v1, v1/2, v2);
            this->SetPrivateExponent(v4 % (v1/2));	// some old keys may have x >= q
        }
        else
        {
            Integer v5(seq);
            this->AccessGroupParameters().Initialize(v1, v2, v3);
            this->SetPrivateExponent(v5);
        }
        
        seq.MessageEnd();
    }
    
    void DEREncode(BufferedTransformation &bt) const
    {
        DERSequenceEncoder seq(bt);
        this->GetGroupParameters().GetModulus().DEREncode(seq);
        if (this->GetGroupParameters().GetCofactor() != 2)
            this->GetGroupParameters().GetSubgroupOrder().DEREncode(seq);
        this->GetGroupParameters().GetGenerator().DEREncode(seq);
        this->GetGroupParameters().ExponentiateBase(this->GetPrivateExponent()).DEREncode(seq);
        this->GetPrivateExponent().DEREncode(seq);
        seq.MessageEnd();
    }
};

//! <a href="http://www.weidai.com/scan-mirror/sig.html#DSA-1363">DSA-1363</a>
template <class H>
struct GDSA : public DL_SS<
DL_SignatureKeys_GFP,
DL_Algorithm_GDSA<Integer>,
DL_SignatureMessageEncodingMethod_DSA,
H>
{
};

//! <a href="http://www.weidai.com/scan-mirror/sig.html#NR">NR</a>
template <class H>
struct NR : public DL_SS<
DL_SignatureKeys_GFP,
DL_Algorithm_NR<Integer>,
DL_SignatureMessageEncodingMethod_NR,
H>
{
};

//! DSA group parameters, these are GF(p) group parameters that are allowed by the DSA standard
class CRYPTOPP_DLL DL_GroupParameters_DSA : public DL_GroupParameters_GFP
{
public:
    /*! also checks that the lengths of p and q are allowed by the DSA standard */
    bool ValidateGroup(RandomNumberGenerator &rng, unsigned int level) const;
    /*! parameters: (ModulusSize), or (Modulus, SubgroupOrder, SubgroupGenerator) */
    /*! ModulusSize must be between DSA::MIN_PRIME_LENGTH and DSA::MAX_PRIME_LENGTH, and divisible by DSA::PRIME_LENGTH_MULTIPLE */
    void GenerateRandom(RandomNumberGenerator &rng, const NameValuePairs &alg);
    
    static bool CRYPTOPP_API IsValidPrimeLength(unsigned int pbits)
    {return pbits >= MIN_PRIME_LENGTH && pbits <= MAX_PRIME_LENGTH && pbits % PRIME_LENGTH_MULTIPLE == 0;}
    
    enum {MIN_PRIME_LENGTH = 1024, MAX_PRIME_LENGTH = 3072, PRIME_LENGTH_MULTIPLE = 1024};
};

template <class H>
class DSA2;

//! DSA keys
struct DL_Keys_DSA
{
    typedef DL_PublicKey_GFP<DL_GroupParameters_DSA> PublicKey;
    typedef DL_PrivateKey_WithSignaturePairwiseConsistencyTest<DL_PrivateKey_GFP<DL_GroupParameters_DSA>, DSA2<SHA> > PrivateKey;
};

//! <a href="http://en.wikipedia.org/wiki/Digital_Signature_Algorithm">DSA</a>, as specified in FIPS 186-3
// class named DSA2 instead of DSA for backwards compatibility (DSA was a non-template class)
template <class H>
class DSA2 : public DL_SS<
DL_Keys_DSA,
DL_Algorithm_GDSA<Integer>,
DL_SignatureMessageEncodingMethod_DSA,
H,
DSA2<H> >
{
public:
    static std::string CRYPTOPP_API StaticAlgorithmName() {return "DSA/" + (std::string)H::StaticAlgorithmName();}
};

//! DSA with SHA-1, typedef'd for backwards compatibility
typedef DSA2<SHA> DSA;

CRYPTOPP_DLL_TEMPLATE_CLASS DL_PublicKey_GFP<DL_GroupParameters_DSA>;
CRYPTOPP_DLL_TEMPLATE_CLASS DL_PrivateKey_GFP<DL_GroupParameters_DSA>;
CRYPTOPP_DLL_TEMPLATE_CLASS DL_PrivateKey_WithSignaturePairwiseConsistencyTest<DL_PrivateKey_GFP<DL_GroupParameters_DSA>, DSA2<SHA> >;

//! the XOR encryption method, for use with DL-based cryptosystems
template <class MAC, bool DHAES_MODE, bool BC_COMPAT = false>
class DL_EncryptionAlgorithm_Xor : public DL_SymmetricEncryptionAlgorithm
{
public:
    bool ParameterSupported(const char *name) const {return strcmp(name, Name::EncodingParameters()) == 0;}
    size_t GetSymmetricKeyLength(size_t plaintextLength) const
    {return plaintextLength + MAC::DEFAULT_KEYLENGTH;}
    size_t GetSymmetricCiphertextLength(size_t plaintextLength) const
    {return plaintextLength + MAC::DIGESTSIZE;}
    size_t GetMaxSymmetricPlaintextLength(size_t ciphertextLength) const
    {return (unsigned int)SaturatingSubtract(ciphertextLength, (unsigned int)MAC::DIGESTSIZE);}
    void SymmetricEncrypt(RandomNumberGenerator &rng, const byte *key, const byte *plaintext, size_t plaintextLength, byte *ciphertext, const NameValuePairs &parameters) const
    {
        const byte *cipherKey, *macKey;
        if (DHAES_MODE)
        {
            macKey = key;
            cipherKey = key + MAC::DEFAULT_KEYLENGTH;
        }
        else
        {
            cipherKey = key;
            macKey = key + plaintextLength;
        }
        
        ConstByteArrayParameter encodingParameters;
        parameters.GetValue(Name::EncodingParameters(), encodingParameters);
        
        xorbuf(ciphertext, plaintext, cipherKey, plaintextLength);
        MAC mac(macKey);
        mac.Update(ciphertext, plaintextLength);
        mac.Update(encodingParameters.begin(), encodingParameters.size());
        if (DHAES_MODE)
        {
            if (BC_COMPAT)
            {
                byte L[4];
                PutWord(false, BIG_ENDIAN_ORDER, L, word32(8 * encodingParameters.size()));
                mac.Update(L, 4);
            }
            
            else
            {
                byte L[8] = {0,0,0,0};
                PutWord(false, BIG_ENDIAN_ORDER, L+4, word32(encodingParameters.size()));
                mac.Update(L, 8);
            }
            
            
        }
        mac.Final(ciphertext + plaintextLength);
    }
    DecodingResult SymmetricDecrypt(const byte *key, const byte *ciphertext, size_t ciphertextLength, byte *plaintext, const NameValuePairs &parameters) const
    {
        size_t plaintextLength = GetMaxSymmetricPlaintextLength(ciphertextLength);
        const byte *cipherKey, *macKey;
        if (DHAES_MODE)
        {
            macKey = key;
            cipherKey = key + MAC::DEFAULT_KEYLENGTH;
        }
        else
        {
            cipherKey = key;
            macKey = key + plaintextLength;
        }
        
        ConstByteArrayParameter encodingParameters;
        parameters.GetValue(Name::EncodingParameters(), encodingParameters);
        
        MAC mac(macKey);
        mac.Update(ciphertext, plaintextLength);
        mac.Update(encodingParameters.begin(), encodingParameters.size());
        if (DHAES_MODE)
        {
            if (BC_COMPAT)
            {
                byte L[4];
                PutWord(false, BIG_ENDIAN_ORDER, L, word32(8 * encodingParameters.size()));
                mac.Update(L, 4);
            }
            
            else
            {
                byte L[8] = {0,0,0,0};
                PutWord(false, BIG_ENDIAN_ORDER, L+4, word32(encodingParameters.size()));
                mac.Update(L, 8);
            }
            
        }
        if (!mac.Verify(ciphertext + plaintextLength))
            return DecodingResult();
        
        xorbuf(plaintext, ciphertext, cipherKey, plaintextLength);
        return DecodingResult(plaintextLength);
    }
};

//! _
template <class T, bool DHAES_MODE, class KDF>
class DL_KeyDerivationAlgorithm_P1363 : public DL_KeyDerivationAlgorithm<T>
{
public:
    bool ParameterSupported(const char *name) const {return strcmp(name, Name::KeyDerivationParameters()) == 0;}
    void Derive(const DL_GroupParameters<T> &params, byte *derivedKey, size_t derivedLength, const T &agreedElement, const T &ephemeralPublicKey, const NameValuePairs &parameters) const
    {
        SecByteBlock agreedSecret;
        if (DHAES_MODE)
        {
            agreedSecret.New(params.GetEncodedElementSize(true) + params.GetEncodedElementSize(false));
            params.EncodeElement(true, ephemeralPublicKey, agreedSecret);
            params.EncodeElement(false, agreedElement, agreedSecret + params.GetEncodedElementSize(true));
        }
        else
        {
            agreedSecret.New(params.GetEncodedElementSize(false));
            params.EncodeElement(false, agreedElement, agreedSecret);
        }
        
        ConstByteArrayParameter derivationParameters;
        parameters.GetValue(Name::KeyDerivationParameters(), derivationParameters);
        KDF::DeriveKey(derivedKey, derivedLength, agreedSecret, agreedSecret.size(), derivationParameters.begin(), derivationParameters.size());
    }
};

//! Discrete Log Integrated Encryption Scheme, AKA <a href="http://www.weidai.com/scan-mirror/ca.html#DLIES">DLIES</a>
template <class COFACTOR_OPTION = NoCofactorMultiplication, bool DHAES_MODE = true>
struct DLIES
: public DL_ES<
DL_CryptoKeys_GFP,
DL_KeyAgreementAlgorithm_DH<Integer, COFACTOR_OPTION>,
DL_KeyDerivationAlgorithm_P1363<Integer, DHAES_MODE, P1363_KDF2<SHA1> >,
DL_EncryptionAlgorithm_Xor<HMAC<SHA1>, DHAES_MODE>,
DLIES<> >
{
    static std::string CRYPTOPP_API StaticAlgorithmName() {return "DLIES";}	// TODO: fix this after name is standardized
};

NAMESPACE_END

#endif
